The invention concerns a toothed belt drive gear for a motor vehicle wheel, especially a pulley wheel for a motorcycle, which is connected rotation-fast with the hub of the drive wheel and which has an outer rotating toothed ring.
The secondary drive with motorcycles, that is the transmission of torque from the gearing exit to the driven rear wheel, generally takes place through a Cardan shaft, a chain or even a toothed belt. The toothed belt drive is especially convenient here, since it practically combines the good transmission characteristics of the chain with the maintenance friendliness and durability of a Cardan drive.
The driven rear wheel has, in addition to the drive gear, on which the toothed belt runs, a braking facility. Either drum brakes with brake drums incorporated into the wheel hub or disk brakes, whose brake disk is likewise fastened rotation-fast with the wheel hub, are used as brakes. For higher demands, disk brakes are preferred which have a better braking performance in comparison with drum brakes and above and beyond this are relatively maintenance-friendly.
The especially promising combination of a toothed belt drive with a disk brake requires, however, that the toothed belt drive gear, also designated as pulley wheel, as well as the brake disk be attached rotation-fast on the hub of the drive wheel. The previously preferred technical solution provides here for arranging the pulley wheel on the one side and the brake disk on the other side of the rear wheel. This construction, however, also produces basic disadvantages: Thus, accessibility of the rims, spokes and hub for the purpose of maintenance and upkeep is made equally difficult from both sides, namely by the pulley wheel on the one hand and by the brake disk on the other. In addition, rear wheels built up in this way are often felt to be unaesthetic. Moreover, maintenance and upkeep are made difficult by the fact that in disassembling and assembling the rear wheel, it is necessary to monitor simultaneously the installation of the toothed belt on the one side and the fitting of the brake disk into the brake caliper on the other side.
With chain drives it has already been attempted to install a brake disk on the rear chain wheel. This solution nevertheless could not be successful, as there existed the danger that the brakes could be fouled by chain grease. One has up until now completely refrained from mounting a brake disk on the pulley wheel of a toothed belt drive, because brake disks become so hot in operation that the toothed belt would be unavoidably subjected to damage by the heat acting on it.